The present invention is a process for the production of selected methoxysilanes in high yield. The process involves reacting methanol with a silazane at a temperature greater than the boiling point of product methoxysilane and less than the temperature of methanol. Under these temperature conditions rapid removal of product methoxysilanes from the reaction mixture occurs minimizing undesirable reactions which can reduce yield of the process. The described process has been found useful for the production of dimethylmethoxysilane, dimethyldimethoxysilane, and methyldimethoxysilane.
Several reports in the literature describe processes for the production of methoxysilanes.
Viswanathan and Van Dyke. J. Chem. Soc. 3:487, 1968, report the preparation of dimethylmethoxysilane in 97% yield by the reaction of methanol with (Me.sub.2,SiH)S.
Nametkin et al., Chem. Abst. 87(29):152309s, 1977, report that the reaction of dimethylchlorosilane with MeOCH.sub.2 Cl and magnesium in the presence of HgCl.sub.2, and Fe in THF gives a 35-76% yield of dimethylmethoxysilane.
Nazran et al., J. Am. Chem. Soc. 106:7267, 1984, report a process giving greater than 95% yield of dimethylmethoxysilane. The process involves the photolysis of dodecamethylcyclohexasilane as a source of dimethylsilylene and the subsequent reaction of the dimethylsilylene with methanol to form dimethylmethoxysilane.
Kotzsch et al., U.S. Pat. No. 4,228,0921, issued Oct. 14, 1980, describes a process for esterification of an organochlorosilane. The process comprises feeding alcohol into a chlorosilane maintained within a reaction zone without the alcohol contacting the chlorosilane in the gas phase. The esterification is performed stepwise with extraction of hydrogen chloride as it is formed. Addition of the alcohol component is through a bottom valve or by immersion of the supply conduit. The process is reported to be useful for production of dimethylmethoxysilane, dimethyldimethoxysilane, and methyldimethoxysilane.
Nashida et al., U.S. Pat. No. 4,851,558, issued July 25, 1989, report a process for the production of alkoxysilanes containing at least one hydrogen bound to the silicon atom. In the described process, chlorosilane is reacted with an alcohol in the co-presence of a solvent having a boiling point higher than and a solvent having a boiling point lower than the boiling point of the objective alkoxysilane. The process is reported capable of producing dimethylmethoxysilane, dimethyldimethoxysilane, and methyldimethoxysilane.
The objective of the present process is to produce selected methoxysilanes, in high yield, from readily available starting materials; without the use of solvents. catalyst, and other components which can create separation and disposal problems. An additional objective is to provide a high yield method for producing the described methoxysilanes, which results in a product low in chloride content. The availability of methoxysilanes with low chloride content is important, since chloride can act as poison for catalysts, for example platinum, used in reactions where the methoxysilane is an intermediate.
The methoxysilanes obtained by the instant process contain reactive methoxy groups and in some cases hydrogen and as such are useful as intermediates for preparing various organic silicon compounds or silicon functional polysiloxanes.